It is often desirable to tow a trailer behind a vehicle to transport goods or equipment, such as hauling boats from a dry storage area to a body of water. It can be more cost effective to purchase a trailer and to transport the boat from dry storage than to pay to store the boat at a marina or other facility by the water. Trailers and trailer frames are also prevalent in the lawn care industry and other areas where there is a great deal of equipment to be moved from site to site. Another instance where trailers are useful is for transporting highway message signs. Advances in the art have enabled portable highway message signs to display infinite numbers of messages and to have stand alone generators for recharging their batteries. These signs are used to alert drivers of traffic conditions, construction sites, and other important road conditions. The location of these signs often varies, and, therefore, portability is an important feature of any sign designed for roadway use. Accordingly, portable highway message signs are usually built with integral trailer frames that allow a vehicle to move the signs between different locations. As long as the size and weight of the material to be transported is not excessive, a trailer is an economical method of increasing cargo capacity. The alternative to adding trailers is to buy trucks with larger payloads, which can be costly.
Two or four wheel trailers constructed for any of the uses described above are usually equipped with brakes for safety purposes. Brakes are often necessary because under normal conditions when the brakes are applied on the towing vehicle, the forward inertia of the trailer adds substantially to the load on the vehicle brakes and may cause the driver to lose control of the towing vehicle or the trailer. A solution to this problem is to provide the trailer with its own set of hydraulic brakes that sense and respond when the brakes are applied to the towing vehicle.
A typical hydraulic brake system consists of a brake actuator assembly having a master cylinder assembly with a master cylinder in a housing and having a linkage connected to the master cylinder, some type of mechanical brakes such as friction brakes located at the wheels to apply the braking force, and hydraulic lines connected between the master cylinder and the mechanical brakes. Movement of the linkage causes a compression stroke in the master cylinder which creates pressure in the hydraulic lines that activates the brakes located at the wheels. Typically, the forward inertia of the trailer toward the towing vehicle causes the brakes on the trailer to be applied in proportion to the manner that the brakes are applied on the towing vehicle. If the towing vehicle is subject to hard braking, the trailer will be subject to hard braking.
On trailers that are provided with a hydraulic brake system, it is often desirable to have a trailer tongue that is removable. The trailer tongue is that portion of a trailer frame that extends toward the towing vehicle and is equipped with a mechanical device suitable for attaching with a towing appendage, such as a ball hitch on the towing vehicle. It is desirable to have a removable trailer tongue for many reasons. First, a removable trailer tongue can reduce the profile of the trailer to lower shipping costs. Second, a removable trailer tongue can help prevent theft of unattended trailers that may have valuable items attached thereto.
In most commonly used hydraulic brake actuator assemblies such as the Demco Model DA66 (available from Dethmers Manufacturing Co., Boyden, Iowa), the linkage also functions as the trailer tongue. The two portions of the brake actuator assembly, the master cylinder assembly and the linkage/tongue, move relative to one another depending on the force of the trailer against the towing vehicle. When the brakes are applied to the towing vehicle, the trailer applies a forward inertial force to the linkage/tongue which causes the two parts of the actuator assembly to move relative to one another to generate hydraulic pressure to the brakes in the trailer wheel assemblies.
In a typical trailer equipped with a hydraulic brake system, the master cylinder assembly is fixedly attached to the trailer and the linkage/tongue has a hitch that connects with the towing vehicle. Accordingly, in order to separate the linkage/tongue from the rest of the trailer, the hydraulic lines have to be disconnected and the master cylinder assembly has to be removed from the trailer tongue. The time and effort involved in removing the master cylinder assembly and in reinstalling it make this undesirable. It is known in the art to connect the hydraulic lines with quick connect couplings in order to easily connect and disconnect the hydraulic lines. The drawback to these devices is that while the quick couplings can be made to prevent fluid from exiting the system, they cannot be made to completely prevent air from entering the system. Accordingly, the hydraulic system must be bled after reconnecting the hydraulic lines in order to assure that no air has entered the hydraulic lines. The introduction of air into the hydraulic lines can create "mushy" brakes or a brake failure which could lead to loss of control of the towing vehicle.
What is needed is a removable trailer tongue, for use with a hydraulic braking system, that does not require disconnection of the hydraulic system or any of its components in order to remove the trailer tongue from the rest of the trailer.